In a wireless communication system, it is required to synchronize a frequency of a Mobile Station (MS) with a frequency of a Base Station (BS). However, there is generally a frequency offset of the MS with respect to the BS due to oscillator drift of the MS, movement of the MS, etc. Therefore, Automatic Frequency Control (AFC), which automatically keeps a receiver of the MS tuned to a frequency of a received radio signal, is necessary in the receiver of the MS.
In general, a local oscillator of the MS is directly adjusted according to a result of a frequency offset estimation in the AFC. However, there will be a large error in the result of the frequency offset estimation in some extremely critical channel conditions, which may cause the local oscillator to drift away.